Axialpiston machine

ABSTRACT

Axial piston machine comprising a drive shaft, a drive mechanism that is connected thereto for conjoint rotation and comprises one or more drive-mechanism pistons, the piston stroke of which can be set by a swash plate, at least one return spring acting on the swash plate and a setting piston supporting on the swash plate, the axial piston machine comprising at least one control or regulating valve or at least one control or regulating unit, characterized in that a setting piston is guided in the connecting plate and a setting lever acts as a coupling member between the setting piston and the swash plate and the setting-piston axis and the setting-lever axis are positioned in a plane E1, in particular in a half plane E1* extending from the drive-shaft axis M.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to German Patent Application No. 10 2019 109 198.5 filed on Apr. 8, 2019 and German Patent Application No. 10 2020 109 134.6 filed on Apr. 2, 2020. The entire contents of the above-listed application is hereby incorporated by reference for all purposes.

The invention relates to an axial piston machine of the swash-plate type, comprising at least one control or regulating valve for setting the swash angle of the swash plate.

The term “axial piston machine” covers both an axial piston pump and an axial piston motor. A special design of an axial piston machine is the swash-plate machine, which comprises a drive mechanism in the form of a drive-mechanism drum, in which a plurality of drive-mechanism pistons are mounted so as to be axially movable in corresponding cylinder bores of the drive mechanism. The drive mechanism is connected to the drive shaft of the axial piston machine for conjoint rotation, which machine is set in rotation by means of mechanical work in the pump operating mode, for example. In pumping operation, from a specific starting position, the pistons perform a lifting motion in parallel with the rotational axis during half a revolution, in order to thereby draw in hydraulic liquid, referred to below as hydraulic oil for improved readability, from the low-pressure side, whereas said pistons perform a lowering motion during the remaining half revolution of a full rotation about the rotational axis, and thereby bring the previously drawn-in hydraulic oil to the high-pressure level and supply said oil to the working output, i.e. the high-pressure side. In the motor operating mode, the operating principle is reversed by a rotational movement of the drive shaft being generated by applying pressure to the drive-mechanism pistons in a controlled manner.

The stroke of the drive-mechanism pistons is determined by the swivel angle of the swash plate, also referred to as a swivel cradle. The drive-mechanism pistons that perform the lifting motion are always oriented in parallel with the drive shaft when said drive shaft rotates and are each pulled or urged into the motion predetermined by the swash plate and the retainer plate by means of a slide shoe, which is articulated to the pistons. The swash plate does not follow the rotational movement of the drive shaft, such that the slide shoes fastened to the piston perform a sliding movement on the surface of the swash plate facing the slide shoes. The stroke of the drive-mechanism pistons used can thus be set by the swivel angle of the swash plate. The maximum stroke of the drive-mechanism pistons results from the maximum possible swivel angle of the swash plate. The minimum stroke of the drive-mechanism pistons results from the minimum possible swivel angle of the swash plate.

Furthermore, there are axial piston machines in which the swash plate is provided to swivel beyond the neutral position, which is known as mooring operation. There are also axial piston machines which can operate in four-quadrant operation. At this point, it should be noted that the invention can also be used in axial piston machines of this kind.

The desired/required value of the swivel angle of the swash plate, which is specified by the control or the regulation, is reached by means of mechanical force transmission by the setting unit acting on the swash plate. The force develops by means of an oil pressure, which is known as the setting pressure, which is applied to the setting piston associated with the setting unit. The pressure level of the setting pressure is predetermined by a control valve arranged hydraulically upstream of the setting unit or a regulating valve arranged hydraulically upstream of the setting unit. There is an oil connection between the setting-pressure output, which is also referred to as the working connection, of the control valve and the so-called setting chamber. In the setting chamber, the above-mentioned application of pressure to the setting piston takes place by means of the hydraulic oil that is under setting pressure.

Furthermore, in addition to the control valve, other purely hydraulic or mechatronic components may be provided which serve to control or regulate the axial piston machine. An example of a purely hydraulic component is a pressure cut-off, which, for example, can be used to limit the output pressure of an axial piston machine operating in pump operation. An example of a mechatronic component is an electrically actuatable pressure-reducing unit. The output pressure of such a pressure-reducing unit may e.g. be supplied to the valve piston of the control valve that predetermines the setting pressure and has a control-pressure connection and a corresponding control surface intended for this purpose.

Since the most compact possible design is sought here, the problem addressed by the present invention can be considered that of providing a suitable solution for arranging and integrating corresponding hydraulic components in or on the axial piston machine.

This problem is solved by an axial piston machine according to the features of claim 1. Advantageous embodiments of the axial piston machine are found in the dependent claims.

The axial piston machine according to the invention comprises a drive shaft and a drive mechanism that is connected thereto for conjoint rotation and comprises one or more drive-mechanism pistons, the piston stroke of which can be set by a swash plate. At least one return spring acts on the swash plate and a setting piston is supported on the swash plate. Furthermore, the axial piston machine comprises at least one control or regulating valve or at least one control or regulating unit. According to the invention, it is then proposed that the setting piston is guided in the connecting plate and a setting lever acts as a coupling member between the setting piston and the swash plate. It is essential here for the setting-piston axis and the setting-lever axis to be positioned in a plane E1. Preferably, the setting-piston axis and the setting-lever axis are positioned in a half plane E1* extending from the drive-shaft axis M.

The setting-piston axis may extend in parallel with the drive-shaft axis, the setting-lever axis being positioned in the plane E1, in particular in a half plane E1* extending from the drive-shaft axis M. It is conceivable for the setting lever to allow for approximately parallel functional positions relative to the drive-shaft axis and/or approximately coaxial functional positions relative to the setting-piston axis. Approximately preferably means an angular deviation from the relevant axis of less than 3°, particularly preferably of less than 2° and ideally of less than 1°.

Proceeding from the generic axial piston machine, for certain types of control or regulation, it may be advantageous for the control or regulating valve which predetermines the setting pressure to be positioned inside the connecting plate of the axial piston machine.

It is particularly advantageous for the control and/or regulating valve to be inserted into the connecting plate from outside, for example to be screwed into a corresponding hole in the connecting plate from outside. For this purpose, it is preferred to provide the relevant control or regulating valve with a cartridge-shaped housing. This allows it to be replaced easily. Different types of valve or regulator can be used without difficulty, depending on the application. The corresponding control or regulating valve is already integrated in the axial piston machine. It is nevertheless possible to replace said valve without opening the axial piston machine, and the axial piston machine nevertheless remains identical. For example, by accordingly installing a volume-flow-rate control valve, a design for regulating the volume flow rate of the axial piston machine can be provided or, however, by accordingly installing a power regulator, a design for regulating the power of the axial piston machine can be provided.

It is further provided according to the invention that one or more additional hydraulic components, in particular valves or regulators, can be stacked on a portion of the connecting-plate lateral surface, in particular on a portion of the connecting plate in the region of the control or regulating valve housed therein, in order to actuate the control or regulating valve and/or to control or regulate the axial piston machine. As a result, very short connection paths are possible when the individual hydraulic components are connected hydraulically. Furthermore, the axial piston machine can be easily equipped with the desired hydraulic components. The proposed construction also allows a particularly compact unit to be designed which can be integrated in a superordinate machine in a space-saving manner.

A particular advantage of the axial piston machine results if, according to a preferred configuration of the invention, at least one regulating axis of the stacked hydraulic components is perpendicular to the drive-mechanism axis of the axial piston machine. Ideally, all the regulating axes of the stacked hydraulic components are perpendicular to the drive-mechanism axis.

The control or regulating valve preferably acts hydraulically on a mechanical adjusting unit, which mechanically initiates swiveling of the swash plate on the basis of the setting pressure of the control valve. For this purpose, the adjusting apparatus preferably comprises a setting lever, which is mechanically connected to the swash plate at one end and to which pressure is applied at the other end by the generated setting pressure of the control valve by means of setting piston fastened to the end. It is advantageous here for the longitudinal axes of the setting lever and/or setting piston and/or control piston of the control or regulating valve to extend in parallel. It is particularly advantageous for the central longitudinal sections of the setting lever, the setting piston and the control or regulating valve as well as the drive mechanism itself to be in a common plane. The same may optionally also apply to the return springs of the swash plate and other components of the axial piston machine.

The hydraulic pilot control of the control or regulating valve for setting the desired swash angle of the swash plate and thus the volume that can be conveyed in pump operation or the power in motor operation takes place, according to a possible configuration of the invention, by means of a pressure-reducing unit, the pressure output of which is connected to the control input of the control valve. It is possible for the pressure-reducing unit to be electromagnetically pilot-controlled in order for it to be possible to accordingly set the starting control pressure prevailing at the control valve. The pressure-reducing unit is mounted on the provided mounting portion on the connecting-plate lateral surface, optionally with additional hydraulic components stacked thereon.

Additional hydraulic components for controlling/regulating the axial piston machine may likewise be attached to the lateral surface of the connecting plate, for example attached to the above-mentioned pressure-reducing unit in a sandwich-like manner. In this case, at least one regulating axis of the stacked hydraulic components, ideally all the regulating axes, extend in parallel with one another and are oriented perpendicularly to the longitudinal axis of the drive shaft.

One or more valves for implementing types of regulation are understood to be additional hydraulic components. In particular, these include such valves for pressure regulation, volume regulation, power regulation, or a combination thereof. Mechanical-hydraulic regulators or, however, electrically hydraulic regulators are conceivable.

A specific example of these additional hydraulic components is, for example, a pressure cut-off, in particular in combination with a load-sensing stage. The load-sensing stage with pressure cut-off can be housed in a compact manner within a twin housing which is located on the housing of the pressure-reducing unit.

In the selected design, it is advantageous for the longitudinal axes of both the pressure-reducing unit and the load-sensing stage as well as the pressure cut-off to extend in parallel with one another, but not to be in the same vertical sectional plane. Specifically, the central longitudinal axis of the pressure-reducing unit is offset from the common central longitudinal sectional plane of the load-sensing stage and the pressure cut-off.

In another advantageous configuration of the invention, the axial piston machine is constructed as a modular kit comprising at least two connecting plates. The at least two available connecting plates allow the axial piston machine to be adapted to the desired type of application in an uncomplicated and rapid manner. In particular, the connecting plate can also be replaced by the customer without any special knowledge.

A crucial advantage of such a kit is that, for example, at least one connecting plate is provided per direction of rotation of the drive shaft. By changing the connecting plate, the axial piston machine can be rapidly and flexibly modified to the desired direction of rotation in pump operation and/or motor operation. In an ideal case, the at least two connecting plates only differ here on account of the situation of the hydraulic connections, i.e. the positioning of the high-pressure and low-pressure connections (suction connection in pump operation), which are arranged such that the position thereof can simply be interchanged for the relevant direction of rotation. Usually, the low-pressure and high-pressure connections in axial piston machines differ in terms of the diameter dimensions.

The advantageous modular concept allows for additional variations in the connecting plate, and therefore the high-pressure and low-pressure connection may be at the end of the axial piston machine that is at the rear in the axial direction in one connecting plate, while another connecting plate has laterally positioned pressure connections. Likewise, the available connecting plates, with or without a drive shaft, may be equipped to connect a downstream machine, in particular an axial piston machine. If the connecting plate comprises a corresponding drive shaft, detachably arranging a flange adapter is useful in order to make it possible to flexibly attach different types of flange.

Other advantages and properties of the invention shall be explained in greater detail in the following with reference to an embodiment shown in the drawings, in which:

FIG. 1 is a longitudinal section along the drive shaft through the axial piston machine according to the invention,

FIG. 2 is a schematic view of the axial piston machine corresponding to the longitudinal section in FIG. 1,

FIG. 3 is another schematic plan view of the axial piston machine,

FIG. 4 is a simplified view of FIG. 3, with regulating axes being marked.

FIG. 1 is an axial longitudinal section through the axial piston machine according to the invention. The invention will be described in the following with reference to an axial piston pump, but it is explicitly noted that the claimed features of the invention can also be used in an axial piston motor, without restriction. Furthermore, it is noted that the features according to the invention can likewise be used for an axial piston machine which can operate in multiple-quadrant operation.

A drive-mechanism drum 2 is arranged on the drive shaft 1 for conjoint rotation, in which drum a plurality of drive-mechanism pistons 3 are inserted in cylinder bores 4 in a drum-revolver-like manner. The drive-mechanism pistons 3 are each supported on the swash plate 6 by a slide shoe 5. The swash plate is supported on the main housing 8 by a compression spring 7. When the drive shaft 1 rotates, the drive-mechanism pistons 3 slide over the sliding surface of the swash plate 6 by means of their slide shoes 5, and this results in a lifting motion of the drive-mechanism pistons 3 on the basis of the swivel angle of the swash plate 6. Depending on the operating mode of the axial piston machine, either pump operation or motor operation, hydraulic energy or mechanical power is generated thereby.

A retaining device ensures that the running surfaces of the slide shoes 5 of the drive-mechanism pistons 3 do not lose contact with the sliding surface of the swash plate 6 even during the suction phase of said pistons. The retaining device consists, inter alia, of a retainer plate 10 and the retainer ball 9, which rests coaxially on the drive shaft 1. Said retainer ball is pushed to the left in the direction of the swash plate 6 by a spring 12 in the drawing plane (plane E1) and, in the configuration shown, in a half plane E1* extending from the drive-shaft axis, and is supported on the retainer plate 10. As a result, the retainer plate 10 is in constant contact with the slide shoes 5 and pushes the running surfaces thereof against the swash plate 6. The drive-mechanism drum 2 is pushed by the central spring 12 in the direction of the control plate 13.

The stroke of the drive-mechanism pistons 3 is predetermined by the swivel angle of the swash plate 6, which can be altered during operation by means of an adjusting apparatus.

The setting lever 21 comprises a spherical end region at either end, one end of the setting lever 21 forming a ball-joint connection with the swash plate 6 and the other end forming a ball-joint connection with the setting piston 22. The setting lever 21 may be designed to be rotationally symmetrical with its longitudinal axis and/or may be designed to be mirror-symmetrical with a vertical axis. The setting lever 21 extends in the axial direction from the swash plate 6, over the control plate 13, and into a blind hole 11 a, which is inside the connecting plate 11 and in which the setting piston 22 is guided.

A control or regulating valve 30 may be housed within the connecting plate 11.

The spherical setting-lever end opposite the swash plate 6 forms a ball-joint connection together with the spherical recess in the setting piston 22. The setting piston 22 is mounted so as to be axially movable within the blind hole 1 lain the connecting plate 11. On its end face opposite the spherical recess, the setting piston 22 shown in the embodiment comprises a small cylindrical projection 23, on which a compression spring of the control or regulating valve 30 can be supported. In such a design, the position of the setting piston 22 exerts a force on this compression spring, which is therefore also referred to as a feedback spring. As a result, the control or regulation to which the control or regulating valve contributes is influenced by the position of the setting piston 22, which is desired for regulating volume flow rate, for example.

Two stops for the setting piston 22 in the region of the blind hole 11 a limit the adjusting movement for the swash plate 6. A first stop for limiting the maximum swivel angle is formed by the base of the blind hole 11 a, such that the maximum slide-in path of the setting lever 21 into the blind hole 11 a is limited here. A second stop for the setting piston 22 for limiting the minimum swivel angle is formed by a flat protrusion of the machine housing 8 in the region of the blind hole 11 a.

The arrangement described makes it possible to utilize the overall length of the connecting plate 11 for housing the control or regulating valve 30. Said valve can be inserted and screwed into the connecting plate 11 from outside such that it is possible to easily replace the valve 30.

In the schematic view in FIG. 2, the axial piston machine is shown with a plurality of attached hydraulic components 50, 51, 52, which are stacked in a sandwich-like manner and are fastened to the connecting plate 11 on the housing side. Such a hydraulic component is also a control valve or regulating valve. In order to better differentiate it from a control or regulating valve 30 which is installed in the connecting plate, such a hydraulic component that is fastened to the outer lateral surface of the connecting plate 11 is referred to as a control or regulating unit. A plurality of control units may also be fastened to the outer lateral surface of the connecting plate 11. Likewise, a plurality of regulating units may be fastened to the outer lateral surface of the connecting plate 11. Equally, a control unit or a plurality of control units comprising a regulating unit or a plurality of regulating units may be fastened to the connecting plate 11 in the position corresponding to the units 50, 51, 52.

Said units 50, 51, 52 mounted on the connecting plate are in the immediate vicinity of the position in which, if present, a control or regulating valve 30 can be screwed into the connecting plate 11. This compact arrangement provides the advantage of short oil connections, which also extend into the solid valve housings or regulator housings and the connecting plate. This results in a sturdy construction, which is clearly advantageous when used in mobile machines, in which there are particularly high and frequently occurring loads due to shocks and vibrations.

A specific example of use of the schematic embodiment shown may be the following arrangement:

The unit 50 fastened directly to the connecting plate may be an electrically actuatable pressure-reducing unit. The desired control pressure is generated at the pressure output there by electrical actuation, which control pressure acts on the valve piston of the control valve 30. The control valve 30 may be a volume-flow-rate control valve. The units fastened above the pressure-reducing unit 50 may be a pressure-cut off 51 and a load-sensing unit 52.

The units 50, 51, 52 that are stacked in a sandwich-like manner can likewise be seen in the plan view in FIG. 3. FIG. 4 again shows the plan view from FIG. 3, but with the control or regulating axes 50 a, 51 a, 52 a of the control or regulating units 50, 51, 52 shown by dashed lines and with the central longitudinal axis of the drive shaft 1 also shown by dashed lines. It can be clearly seen that all of said axes 50 a, 51 a, 52 a of the units 50, 51, 52 are perpendicular to the longitudinal axis of the drive shaft 2. It can also be clearly seen that, in the embodiment, the respective longitudinal axes of the drive shaft 1, the setting lever 21, the setting piston 22 and the regulating or setting valve are all in a common half plane E1*. The half plane E1* is delimited by the longitudinal axis of the drive shaft. Irrespective of the position of the setting piston, this is always the same half plane E1*.

Furthermore, it can be seen from FIG. 4 that all the control or regulating axes 52 a, 51 a, 50 a of the units 52, 51, 50 extend in parallel with one another in pairs.

The control or regulating units 50, 51, 52 can be used irrespective of the direction of rotation of the drive shaft or of the drive mechanism. If the direction of rotation is changed, these units merely need to be rotated by 180° relative to their longitudinal direction.

Other advantages of the structural arrangement relating to the axial piston machine according to the invention are as follows:

Owing to the low angular change of the setting lever 21 relative to the central axis of the setting piston 22, force transmission in the region of the setting piston 22 that is almost free of lateral forces is achieved. Inserting the spherical region of the setting lever 21 into the inner region of the setting piston 22 also contributes to this.

It is particularly advantageous to evenly load the swash-plate mount 40 by means of the forces from the adjusting apparatus that are introduced centrally with respect to the mounting points.

The arrangement of the control or regulating valves and the control or regulating units ensures that the installation space required for tandem operation of a plurality of axial piston machines is not obstructed by said valves or units.

List of reference characters: Drive shaft 1 Drive-mechanism drum 2 Drive-mechanism piston 3 Cylinder bores 4 Slide shoe 5 Swash plate 6 Compression spring 7 Main housing 8 Retainer ball 9 Retainer plate 10  Connecting plate 11  Blind hole 11a Spring 12  Control plate 13  Setting lever 21  Setting piston 22  Cylindrical projection 23  Control or regulating valve 30  Swash-plate mount 40  Pressure-reducing unit 50  Control or regulating axis 50a Pressure cut-off 51  Control or regulating axis 51a Load-sensing unit 52  Control or regulating axes 52a Plane E1  Half plane E1* 

1. Axial piston machine comprising a drive shaft, a drive mechanism that is connected thereto for conjoint rotation and comprises one or more drive-mechanism pistons, a piston stroke of which can be set by a swash plate, wherein at least one return spring acts on the swash plate and a setting piston is supported on the swash plate, wherein the axial piston machine comprises at least one control or regulating valve or at least one control or regulating unit, wherein a setting piston is guided in a connecting plate and a setting lever acts as a coupling member between the setting piston and the swash plate and a setting-piston axis and a setting-lever axis are positioned in a plane.
 2. Axial piston machine according to claim 1, wherein the setting-lever axis are positioned in a plane, the plane being a half plane extending from a drive-shaft axis, and wherein the setting-piston axis extends in parallel with the drive-shaft axis and the setting-lever axis is positioned in the plane.
 3. Axial piston machine according to claim 2, wherein the setting lever allows for approximately parallel functional positions relative to the drive-shaft axis and/or approximately coaxial functional positions relative to the setting-piston axis, wherein an angular deviation from the relevant axis of less than 3° is made possible.
 4. Axial piston machine according to claim 3, wherein an extension of a central axis of the at least one return spring is positioned in the plane.
 5. Axial piston machine according to claim 4, wherein the half plane extends centrally or almost centrally with respect to a swash-plate mount.
 6. Axial piston machine according to claim 2, wherein a control or regulating valve is in the connecting plate, wherein the axis of said control or regulating valve is positioned in the half plane and the axis of said control or regulating valve is arranged in parallel with the drive shaft.
 7. Axial piston machine according to claim 2, wherein at least one control or regulating unit is arranged on the connecting plate, wherein an axis of the control or regulating unit extends approximately at right angles to the half plane.
 8. Axial piston machine according to claim 7, wherein a plurality of the control or regulating units are arranged on the connecting plate, wherein each axis of such control or regulating unit extends either approximately at right angles to the half plane or approximately in parallel with the half plane.
 9. Axial piston machine according to claim 6, wherein each axis of the control or regulating valves installed in the connecting plate is approximately at right angles to at least one axis of a control or regulating unit arranged on the connecting plate. 